<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>
	<body>
		
		<script>
			
			
			//Math 不需要new  内置函数
			
			var random =Math.random();
			console.log(random);
			
			var pi = Math.PI;
			console.log(pi);
			
			var sin90 = Math.sin(Math.PI/6);
			console.log(sin90);
			
			var cos90 = Math.cos(Math.PI/6);
			console.log(cos90);
			
			var tan = Math.tan(Math.PI/6);
			console.log(tan);
			
			console.log(Math.pow(2,3));
			
			console.log(Math.sqrt(16));
			
			
			var xx  = "abc@@123";
			
			var index =xx.indexOf('@');
			
			if()
			console.log(index);
			
			
		</script>
	</body>
</html>
